As a first example of a usual freely opening and closing type communication terminal, a communication terminal is disclosed in Patent Document 1. Here, the communication terminal is described by using the drawings. FIG. 20 is a view showing the structure of the usual communication terminal and a principle of an operation of an antenna provided therein. FIG. 20(a) shows a state that a casing is closed and FIG. 20(b) shows a state that the casing is opened. In FIGS. 20(a) and 20(b), the communication terminal includes a first casing 202 connected to an antenna 201 capable of being pulled out and a second casing 203 located in the side surface of the antenna 201 upon using and made of metal or a material including metal. The first casing 202 is connected to the second casing 203. In this communication terminal, high frequency electric current supplied to the first casing 202 having the antenna 201 is also supplied to the casing 203. The directions of the electric current at this time are shown by arrow marks G, H, I and J.
As a second example of a usual freely opening and closing type communication terminal, Patent Document 2 discloses a communication terminal in which a first casing having an antenna provided in one end side is connected to a second casing through a hinge part at the other end side so as to freely open and close and a spirally wound flexible base is disposed in the hinge part. FIG. 21 is a view showing the change of the flexible base in accordance with opening and closing operations when the flexible base is spirally wound and provided in the usual communication terminal. FIG. 21(a) shows a state that the casings are opened and FIG. 21(b) shows a state that the casings are closed. In the flexible base 204 shown in FIG. 21(a), a full line shows a state when the casings are opened. A two-dot chain line shows a case when the casings are closed not to change an angle of torsion.
(Patent Document 1)
JP-A-2002-33804
(Patent Document 2)
JP-A-6-311216
However, in the usual communication terminal of the first example, since the first and second casings 202 and 203 are connected together, when the casings are closed, the electric current supplied to each of the casings 202 and 203 has the same phase (the arrow marks G and H have the same directions). That is, the electric current flows from an end side in which the antenna 201 is provided to an opposite end side. When the two casings 202 and 203 are opened, casing current (an arrow mark I) supplied to the first casing 202 is not changed from casing current (an arrow mark G) when the casings are closed. However, the direction of casing current (an arrow mark J) supplied to the second casing 203 is different from the direction of the casing current (an arrow mark I) supplied to the first casing 202 (opposite phase). Accordingly, when a casing closing state is changed to a casing opening state, radiation efficiency may be probably undesirably deteriorated.
Further, in the usual communication terminal of the second example, the antenna protrudes from the casing. In the protruding antenna as described above, when a user takes out the communication terminal accommodated in a pocket, the antenna is inconveniently hooked on the edge part of the pocket. Accordingly, in recent years, even an opening and closing type or collapsible communication terminal having a hinge part has been desired to incorporate an antenna therein.
Further, as shown in FIG. 21, the spirally wound flexible base 204 has a structure in which a bending stress and a torsion stress are generated in accordance with the opening and closing operations of the casings. Thus, a conductor part (a circuit pattern) of the flexible base 204 may be possibly cut. That is, in order to prevent an angle of torsion P of the flexible base wound clockwise from a lower side to an upper side from changing, when the flexible base 204 is wound as shown by the two-dot chain line in FIG. 21(a), the generation of the torsion stress can be avoided. However, in both the ends of the flexible base 204, positions (both side directions of right and left) where the flexible base is fixed to the two casings do not change even when the casings are opened or closed. Accordingly, a state that the casings are opened is changed to a state that the casings are closed as shown by a full line in FIG. 21(b), the angle of torsion is changed to about P/2. Therefore, both the bending stress and the torsion stress are exerted on the flexible base 204 in accordance with the opening and closing operations of the casings.
Ordinarily, the flexible base has an adequately strong structure relative to the bending stress, because the flexible base has flexibility. However, when various compound stresses act on the flexible base, a disconnection or a break is caused. Accordingly, in the usual communication terminal, when the opening and closing operations of the casings are repeated, the disconnection or the break of the flexible base may be possibly caused. Thus, there is room for improvement in this respect.
The present invention is proposed by considering the above-described problems and it is an object of the present invention to provide a communication terminal that can suppress the deterioration of a gain of an antenna either in an opening state or in a closing state.